Altered central sensorimotor processing in patients with complex regional pain syndrome

Abstract

Alterations in tactile sensitivity are common in patients with chronic pain. Recent brain imaging studies have indicated that brain areas activated by acute experimental pain partly overlap with areas processing innocuous tactile stimuli. However, the possible effect of chronic pain on central tactile processing has remained unclear. We have examined, both clinically and with whole-head magnetoencephalography, six patients suffering from complex regional pain syndrome (CRPS) of the upper limb. The cortical somatosensory responses were elicited by tactile stimuli applied to the fingertips and the reactivity of spontaneous brain oscillations was monitored as well. Tactile stimulation of the index finger elicited an initial activation at 65 ms in the contralateral SI cortex, followed by activation of the ipsi- and contralateral SII cortices at about 130 ms. The SI responses were 25-55% stronger to stimulation of the painful than the healthy side. The distance between SI representations of thumb and little finger was significantly shorter in the hemisphere contralateral than ipsilateral to the painful upper limb. In addition, reactivity of the 20-Hz motor cortex rhythm to tactile stimuli was altered in the CRPS patients, suggesting modified inhibition of the motor cortex. These results imply that chronic pain may alter central tactile and motor processing.

Wherever is my arm? Impaired upper limb position accuracy in Complex Regional Pain Syndrome

“…Two participants also depicted distortions of the unaffected side. As there was no known CRPS pathology of the unaffected side, these distortions could possibly be explained by altered central processing within cortical centres responsible for limb representation as demonstrated by brain imaging studies [25,27,28,34]. It is acknowledged that this unvalidated measure was devised specifically for this study hence these results are exploratory.…”

“…Body perception disturbances, specifically distortions in mental image, as well as cortical remapping in body schema associated regions, are indicative of body schema disruption [11,13,14,25,26,27,28,31,32,34]. Consequently, an anatomically distorted affected limb schema would provide incorrect reference information for movement planning [33].…”

Imaging and Clinical Evidence of Sensorimotor Problems in CRPS: Utilizing Novel Treatment Approaches

“…For example shrinkage in cortical representation of the affected limb is known to occur within the primary somatosensory cortex (SI) (Juottonen et al 2002;Maihofner et al 2003;Maihofner et al 2004;Pleger et al 2005;Pleger et al 2006). SI is responsible for processing tactile inputs and provides a central somatosensory representation of the body surface.…”

Functional Imaging of Central Nervous System Involvement in Complex Regional Pain Syndrome

“…This study was followed by a number of studies dealing with an altered central somatosensory network in CRPS. To examine possible alterations in the central processing of tactile stimuli, Juottonen et al 20 used MEG to assess somatosensory-evoked fields in response to tactile stimulation applied to the tip of the thumb, the index finger, and the little finger in patients with CRPS I of the hand. They found a significantly stronger response in the contralateral primary somatosensory cortex (S1) and a nonsignificant tendency toward a stronger response in the contralateral secondary somatosensory cortex (S2) after stimulation of the index fin-ger of the affected hand compared with the unaffected hand.…”